Nociceptin/orphanin FQ (N/oFQ), a recently isolated neuropeptide is the endogenous ligand of the opioid receptor-like1 (ORL1) receptor. Preliminary data supporting this application suggest that ORL1 agonists produce functional anti-opioid as well as functional anti-CRF effects. Considering that antagonism of opioid and CRF transmission is known to block the respective effects of two important risk factors for relapse -- stress and alcohol cue exposure - in animal models of relapse, this dual action of ORL1 agonists identifies the N/oFQ-ORL1 system as a highly promising target for "anti-relapse" medications. This present proposal was, therefore, developed to systematically investigate the role of the N/oFQ-ORL1 system in the regulation of ethanol-seeking behavior, with two related major goals. The first goal (to be pursued in Specific Aim 1) is to establish that the ORL1 receptor represents an effective treatment target for relapse prevention by studying the effects of a novel, selective non-peptide ORL1 receptor agonist Ro 64-6198 on reinstatement of ethanol-seeking induced by stress and ethanol cues and by comparing the effects of this agent to those of a CRF antagonist, a benzodiazepine, and an opiate antagonist (i.e., agents with established anti-stress, anxiolytic, or anti-craving action). The second goal (to be pursued in Specific Aims 2 - 4) is to elucidate the neurobiological basis for the regulation of stress and alcohol cue-induced ethanol-seeking by the N/oFQ-ORL1 system at the neuroanatomical, neurocircuitry, and neurochemical level. All Specific Aims will include an additional set of objectives which is to provide insight into neuroadaptive changes in the N/oFQ-ORL1 system that may underlie the development of vulnerability to relapse following chronic ethanol exposure, and into innate dysregulations of this systems that may convey heightened susceptibility to the motivating effects of stress and alcohol cue exposure. For this purpose, data will be generated in and compared among rats differing in ethanol history or genetically-determined ethanol preference and, thus, presumably in the degree of motivation to engage in ethanol-seeking behavior. These subject populations include (1) genetically heterogeneous Wistar rats with a history of daily limited-access ethanol self-administration, (2) Wistar rats with a history of prior ethanol dependence, but tested 3 - 4 weeks following withdrawal (i.e., during the "protracted withdrawal" phase), and (3) genetically selected Marchigian Alcohol Preferring (msP) rats, a line of rats that has been proposed to represent an animal model of genetic vulnerability to relapse. Novel information on ethanoI-N/oFQ interactions at the systems level, and interactions with other neurochemical systems in regulating ethanol-seeking behavior to be generated by these studies is expected to aid in developing "anti-relapse" treatments aimed at the N/oFQ-ORL1 receptor system or related pharmacological targets.